CYP2C19 pharmacogenomics associated with therapy of Helicobacter pylori infection and gastro-esophageal reflux diseases with a proton pump inhibitor

Crises in Antimicrobial Stewardship: Misuse of Clarithromycin for Helicobacter pylori Therapy

Helicobacter pylori is a class I carcinogen that infects more than 100 million individuals in the United States. Antimicrobial therapy for H. pylori has typically been prescribed empirically rather than based on susceptibility testing. Until recently, therapeutic recommendations have generally ignored the principles of antibiotic stewardship. A combination of a proton pump inhibitor (PPI), amoxicillin, and clarithromycin (triple therapy) remains popular despite increasing clarithromycin resistance and poor cure rates. Concomitant therapy (a PPI, amoxicillin, clarithromycin, and metronidazole) is recommended and widely used despite all patients receiving at least one unneeded antibiotic. In 2020, the Food and Drug Administration approved vonoprazan, amoxicillin, and clarithromycin triple therapy, which administers unneeded clarithromycin to >90% of patients (i.e., ~6 tons of unneeded clarithromycin/million treatments). In the late 1980s, the infectious disease community functionally transferred responsibility for the management of H. pylori to gastroenterology, which has managed the infection as another common gastrointestinal disease such as constipation. In 2022, both traditional and noninvasive molecular-based susceptibility testing for H. pylori became available in the United States. In order to reduce and prevent antibiotic misuse, the infectious disease community should reclaim responsibility for the management of this important infectious disease.

Refractory Gastroesophageal Reflux Disease: Diagnosis and Management

Gastroesophageal reflux disease (GERD) is common, with increasing worldwide disease prevalence and high economic burden. A significant number of patients will remain symptomatic following an empiric proton pump inhibitor (PPI) trial. Persistent symptoms despite PPI therapy are often mislabeled as refractory GERD. For patients with no prior GERD evidence (unproven GERD), testing is performed off antisecretory therapy to identify objective evidence of pathologic reflux using criteria outlined by the Lyon consensus. In proven GERD, differentiation between refractory symptoms (persisting symptoms despite optimized antisecretory therapy) and refractory GERD (abnormal reflux metrics on ambulatory pH impedance monitoring and/or persistent erosive esophagitis on endoscopy while on optimized PPI therapy) can direct subsequent management. While refractory symptoms may arise from esophageal hypersensitivity or functional heartburn, proven refractory GERD requires personalization of the management approach, tapping from an array of non-pharmacologic, pharmacologic, endoscopic, and surgical interventions. Proper diagnosis and management of refractory GERD is critical to mitigate undesirable long-term complications such as strictures, Barrett's esophagus, and esophageal adenocarcinoma. This review outlines the diagnostic workup of patients presenting with refractory GERD symptoms, describes the distinction between unproven and proven GERD, and provides a comprehensive review of the current treatment strategies available for the management of refractory GERD.

Efficacy of Treatment with and without Initial Clopidogrel Loading in Branch Atheromatous Disease

Objective Despite aggressive therapeutic interventions during the acute phase of branch atheromatous disease (BAD)-type cerebral infarction, many patients, even those with a mild condition at the onset, experience neurological deterioration after hospitalization and develop serious deficits. We compared the therapeutic efficacy of multiple antithrombotic therapies for BAD between patients who received a clopidogrel loading dose (loading group; LG) and those without loading (non-loading group; NLG). Patients Between January 2019 and May 2022, patients with BAD-type cerebral infarction in the lenticulostriate artery admitted within 24 h of the onset were recruited. This study included 95 consecutive patients who received combination argatroban and dual antiplatelet therapy (aspirin and clopidogrel). Methods Patients were classified into the LG and NLG according to whether or not a loading dose of clopidogrel (300 mg) had been administered on admission. Changes in neurological severity [National Institutes of Health Stroke Scale (NIHSS) score] during the acute phase were retrospectively evaluated. Results There were 34 (36%) and 61 (64%) patients in the LG and NLG, respectively. On admission, the median NIHSS score was similar between the groups [LG: 2.5 (2-4) vs. NLG: 3 (2-4), p=0.771]. At 48 h following admission, the median NIHSS scores were 1 (0.25-4), and 2 (1-5) in the LG and NLG, respectively (p=0.045). Early neurological deterioration (END; defined as worsening of the NIHSS score by ≥4 points at 48 h after admission) occurred in 3% of LG and 20% of NLG patients (p=0.028). Conclusion Administration of a clopidogrel loading dose with combination antithrombotic therapy for BAD reduced END.

Effects of CYP2C19 genetic polymorphisms on the cure rates of H. pylori in patients treated with the proton pump inhibitors: An updated meta-analysis

Background: The cure rates of Helicobacter pylori (H. pylori) treatment using a proton pump inhibitor (PPI) are gradually decreasing due to antibiotic resistance, poor compliance, high gastric acidity, and cytochrome P450 2C19 (CYP2C19) polymorphism, and the effects of PPI depend on metabolic enzymes, cytochrome P450 enzymes. The aim of this meta-analysis was to determine whether CYP2C19 polymorphisms affect H. pylori cure rates in patients treated with different proton pump inhibitors (PPIs) according to stratified analysis.

Materials and methods: The literature was searched with the key words “H. pylori” and “CYP2C19” in PubMed, CNKI, and Wanfang up to 31 May 2022, and the studies were limited to clinical observational or randomized controlled trials (RCTs). Finally, seven RCTs and 29 clinical observational studies met the inclusion criteria and were used for the meta-analysis via STATA version 16.

Results: The cure rates were significantly different between genotypes of homozygous extensive metabolizers (EM) and poor metabolizers (PM) (OR = 0.58, 95% CI: 0.47–0.71) and between EM and heterozygous extensive metabolizers (IM) (OR = 0.71, 95% CI: 0.59–0.86), but not between IM and PM. Moreover, there was a significantly lower H. pylori cure rate in EM subjects than that in IM subjects when treated with omeprazole (66.4% vs. 84.1%), lansoprazole (76.1% vs. 85.6%), but not rabeprazole, esomeprazole, or pantoprazole. In addition, there was a significantly lower H. pylori cure rate in EM subjects than that in IM subjects when treated with a PPIs for 7 days (77.4% vs. 82.1%), but not 14 days (85.4% vs. 90.0%).

Conclusion: Carriers of CYP2C19 loss-of-function variant alleles (IM and PM) exhibit a significantly greater cure rate of H. pylori than noncarriers (EM) regardless of other factors (84.7% vs. 79.2%). In addition, pantoprazole- and rabeprazole-based quadruple therapy for H. pylori treatment is less dependent on the CYP2C19 genotype and should be prioritized in Asian populations with H. pylori.

Two-dimension Tailor-made Therapy: A New Salvage Therapy After Multiple Eradication Failures for Helicobacter pylori Infection

Background and Aims

Vonoprazan-based eradication therapies have a higher eradication rate than usual proton pump inhibitor (PPI)-based therapies in treating Helicobacter pylori infection. Should we use vonoprazan to treat patients who failed multiple eradication therapies? Because the drug is not available in most countries, we propose 2-dimension tailor-made therapy (2dTMT) without using vonoprazan.

Methods

Patients who failed twice or more PPI-based triple therapies were recruited. Patients underwent CYP2C19 genotype and antibiotic susceptibility tests (ASTs). PPI doses per day were decided as per the CYP2C19 genotype: twice for poor and 4 times for extensive metabolizers (dimension 1). Two antibiotics were selected as per the results of the AST in each patient (dimension 2). Regimens of 2dTMT included 2 susceptible antibiotics and a PPI. For those who could not have enough information with the AST, tailor-made PPI dosing was indicated with empirically selected 2 antibiotics (one-dimension tailor-made therapy [1dTMT]).

Results

Of 51 candidates with multiple eradication failures, 37 patients underwent the genotype test and AST, and 24 succeeded to obtain sufficient information to select 2 susceptible antibiotics. Of them, 22 patients accepted to receive 14-day 2dTMT. Of the residual patients, 12 accepted to receive 14-day 1dTMT. The mean eradication rate of 2dTMT was 86.4% (95% confidence interval [CI]: 65.1%-98.8%) in intention-to-treat and 90.5% (95% CI: 69.6%-98.8%) in per-protocol analyses, whereas that of 1dTMT was 75.0% (95% CI: 42.8%-94.5%) in intention-to-treat and 90.0% (95% CI: 55.5%-99.7%) in per-protocol analyses.

Conclusion

Without vonoprazan, 14-day 2dTMT could be one of the salvage therapies for patients with multiple eradication failures. In cases of insufficient information with the AST, 14-day 1dTMT could be an alternative therapy. Clinical Trials Registry number, UMIN000022154 (https://www.umin.ac.jp/icdr/index.html).

Efficacy and safety of bismuth quadruple regimens containing tetracycline or furazolidone for initial eradication of Helicobacter pylori

Helicobacter pylori (H pylori) infection can cause chronic gastritis, peptic ulcer, and even gastric cancer, so effective eradication is critical.This study compared the efficacy and safety of bismuth quadruple regimens including either tetracycline or furazolidone for initial eradication.Patients newly diagnosed with H pylori infection from January 2020 to January 2021 were randomly assigned to receive either the tetracycline-containing regimen (n = 116) or furazolidone-containing regimen (n = 168). Both regimens included 1 proton pump inhibitor (rabeprazole 20 mg, or esomeprazole 20 mg, or eprazole 5 mg), colloidal pectin bismuth 300 mg, and amoxicillin 1000 mg in addition to tetracycline 1.0 g or furazolidone 0.1 g. All drugs were administered twice daily for 12 consecutive days. The 14C urea breath test was used for diagnosis, and re-test negativity at one-month follow-up was considered successful eradication. Adverse events were recorded during follow-up by telephone interview.In total, 109 patients in the tetracycline group and 157 in the furazolidone group were re-examined at 1 month. In the tetracycline group, 101 patients tested negative at follow-up, yielding an eradication rate of 92.7% according to per-protocol analysis and 87.1% by intention-to-treat analysis. In the furazolidone group, 141 patients tested negative, yielding eradication rates of 89.8% by PP and 83.9% by ITT. Eradication rates did not differ significantly between regimens (per-protocol: χ2 = 0.637, P = .517; intention-to-treat: χ2 = 0.537, P = .501). However, total adverse events incidence was significantly lower in the tetracycline group (20.2% vs 37.6%; χ2 = 9.193, P = .003).Both bismuth quadruple regimens produce high initial eradication, but the tetracycline regimen appears safer.

Effects of Genetic Polymorphisms of Cathepsin A on Metabolism of Tenofovir Alafenamide

Cathepsin A (CatA) is important as a drug-metabolizing enzyme responsible for the activation of prodrugs, such as the anti-human immunodeficiency virus drug Tenofovir Alafenamide (TAF). The present study was undertaken to clarify the presence of polymorphisms of the CatA gene in healthy Japanese subjects and the influence of gene polymorphism on the expression level of CatA protein and the drug-metabolizing activity. Single-strand conformation polymorphism method was used to analyze genetic polymorphisms in healthy Japanese subjects. Nine genetic polymorphisms were identified in the CatA gene. The polymorphism (85_87CTG>-) in exon 2 was a mutation causing a deletion of leucine, resulting in the change of the leucine 9-repeat (Leu9) to 8-repeat (Leu8) in the signal peptide region of CatA protein. The effect of Leu8 on the expression level of CatA protein was evaluated in Flp-In-293 cells with a stably expressed CatA, resulting in the expression of CatA protein being significantly elevated in variant 2 with Leu8 compared with Leu9. Higher concentrations of tenofovir alanine (TFV-Ala), a metabolite of TAF, were observed in the Leu8-expressing cells than in the Leu9-expressing cells using LC/MS/MS. Our findings suggest that the drug metabolic activity of CatA is altered by the genetic polymorphism.

Refractory Gastroesophageal Reflux Disease: A Management Update

Gastroesophageal reflux disease (GERD) is one of the most frequent gastrointestinal disorders. Proton pump inhibitors (PPIs) are effective in healing lesions and improving symptoms in most cases, although up to 40% of GERD patients do not respond adequately to PPI therapy. Refractory GERD (rGERD) is one of the most challenging problems, given its impact on the quality of life and consumption of health care resources. The definition of rGERD is a controversial topic as it has not been unequivocally established. Indeed, some patients unresponsive to PPIs who experience symptoms potentially related to GERD may not have GERD; in this case the definition could be replaced with “reflux-like PPI-refractory symptoms.” Patients with persistent reflux-like symptoms should undergo a diagnostic workup aimed at finding objective evidence of GERD through endoscopic and pH-impedance investigations. The management strategies regarding rGERD, apart from a careful check of patient's compliance with PPIs, a possible change in the timing of their administration and the choice of a PPI with a different metabolic pathway, include other pharmacologic treatments. These include histamine-2 receptor antagonists (H2RAs), alginates, antacids and mucosal protective agents, potassium competitive acid blockers (PCABs), prokinetics, gamma aminobutyric acid-B (GABA-B) receptor agonists and metabotropic glutamate receptor-5 (mGluR5) antagonists, and pain modulators. If there is no benefit from medical therapy, but there is objective evidence of GERD, invasive antireflux options should be evaluated after having carefully explained the risks and benefits to the patient. The most widely performed invasive antireflux option remains laparoscopic antireflux surgery (LARS), even if other, less invasive, interventions have been suggested in the last few decades, including endoscopic transoral incisionless fundoplication (TIF), magnetic sphincter augmentation (LINX) or radiofrequency therapy (Stretta). Due to the different mechanisms underlying rGERD, the most effective strategy can vary, and it should be tailored to each patient. The aim of this paper is to review the different management options available to successfully deal with rGERD.

Extrahepatic cytochrome P450 epoxygenases: pathophysiology and clinical significance in human gastrointestinal cancers

Cytochrome P450 (CYP) epoxygenases, a multi-gene superfamily of heme-containing enzymes, are commonly known to metabolize endogenous arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs). The role of CYPs is mostly studied in liver drugs metabolism, cardiac pathophysiology, and hypertension fields. Particularly, the biological functions of these enzymes have increasingly attracted a growing interest in cancer biology. Most published studies on CYPs in cancer have been limited to their role as drug metabolizing systems. The activity of these enzymes may affect drug pharmacokinetics and bioavailability as well as exogenous compounds turnover. Some CYP isoforms are selectively highly expressed in tumors, suggesting a potential mechanistic role in promoting resistance to chemotherapy. Majority of drugs elicit their effects in extrahepatic tissues whereby their metabolism can significantly determine treatment outcome. Nonetheless, the role of extrahepatic CYPs is not fully understood and targeting these enzymes as effective anti-cancer therapies are yet to be developed. This review article summarizes an up-to-date body of information from published studies on CYP enzymes expression levels and pathophysiological functions in human normal and malignant gastrointestinal (GI) tract tissues. Specifically, we reviewed and discussed the current research initiatives by emphasizing on the clinical significance and the pathological implication of CYPs in GI malignancies of esophagus, stomach, and colon.

Proton pump inhibitor use is associated with hip fracture development: a nationwide population-based cohort study

BACKGROUND/AIMS

Effect of proton pump inhibitor (PPI) use on the risk of hip fracture is controversial. This study aimed to clarify the association between PPI use and hip fracture risk using a large cohort.

METHODS

This study recruited participants from the nationwide cohort (n = 1,025,340). After exclusion of participants who had hip fractures or were aged less than 40 years during the baseline period (2002 to 2004), 371,806 participants were followed to 2013. Participants prescribed PPIs for more than 90 days during baseline period were defined as users. Fracture cases were defined when participants were hospitalized with claims of a hip fracture.

RESULTS

During 4,159,343 person-years of follow-up, fractures developed more often in PPI users than in nonusers (relative risk [RR], 1.787; 95% confidence interval [CI], 1.260 to 2.534; p = 0.002). The results persisted after adjusting for age, sex, and many drugs relevant to osteoporosis or influential in bone health. Furthermore, fracture risk associated with PPI use increased with duration of use (p trend < 0.001). The fully adjusted RRs of hip fracture development were 1.350 (95% CI, 1.203 to 1.515) for 1- to 90-day users, 1.487 (95% CI, 0.957 to 2.311) for 91- to 180-day users, and 1.771 (95% CI, 0.931 to 3.368) for > 180-day users. The positive association between PPI use and fracture was also confirmed in a subgroup with health screening data where further adjustment for body mass index, smoking status, alcohol consumption, and physical activity was available (adjusted RR, 2.025; 95% CI, 1.151 to 3.564, p = 0.014).

CONCLUSION

PPI use is associated with hip fracture development.

CYP2C19 genotype-guided antiplatelet therapy: promises and pitfalls

Pharmacogenetic variants can alter the mechanism of action (pharmacodynamic gene variants) or kinetic processes such as absorption, distribution, metabolism and elimination (pharmacokinetic gene variants). Many initial successes in precision medicine occurred in the context of genes encoding the cytochromes P450 (CYP enzymes). CYP2C19 activates the antiplatelet drug clopidogrel, and polymorphisms in the CYP2C19 gene are known to alter the outcome for patients taking clopidogrel in the context of cardiovascular disease. CYP2C19 loss-of-function alleles are specifically associated with increased risk for coronary stent thrombosis and major adverse cardiovascular events in patients taking clopidogrel following percutaneous coronary intervention. We explore successes and challenges encountered as the clinical and scientific communities advance CYP2C19 genotyping in the context of routine patient care.

Personalized therapy for Helicobacter pylori: CYP2C19 genotype effect on first-line triple therapy

BACKGROUND

Triple therapy efficacy against Helicobacter pylori is low worldwide, and thus, alternatives must be sought to improve eradication. The aim of the present study was to determine CYP2C19 genetic polymorphism effect on H pylori eradication.

METHODS

A randomized, single-blinded clinical trial including 133 participants was carried out. H pylori infection was confirmed by histologic and microbiologic test. Antibiotic susceptibility to amoxicillin and clarithromycin was performed. CYP2C19 polymorphisms *1, *2, and *3 were analyzed by real-time PCR (Roche ®), and nested PCR for CYP2C19*17 polymorphisms. Participants were randomized into two groups for different H pylori therapies, one with standard omeprazole doses and another with omeprazole doses depending on CYP2C19 polymorphism. H pylori eradication was verified by stool antigen tests (Meridian ®).

RESULTS

The most common CYP2C19 polymorphism was *1/*1 in 54.9% of the participants followed by *17/*17 in 21.1%. Triple therapy efficacy with standard omeprazole doses versus personalized therapy based on CYP2C19 polymorphism by ITT analysis was 84% (95% CI: 0.73-0.91) vs 92.2% (95% CI: 0.82-0.97) (P = 0. 14), respectively. The efficacy by PP analysis was 92.1% (95% CI: 0.82-0.97) vs 100% (95% CI: 0.92-0.01) (P = 0.027), respectively.

CONCLUSIONS

The most frequent polymorphism was extensive PPI metabolizers (62.4%). Effectiveness of guided therapies by susceptibility test was good, yet they can be further improved by customized therapy based on CYP genotype. Therefore, high PPI (80 mg/d) doses are recommended for H pylori eradication therapies in Colombia. ClinicalTrials.gov ID: NCT03650543.

Proton pump inhibitors: from CYP2C19 pharmacogenetics to precision medicine

Introduction: Proton Pump inhibitors (PPIs) are commonly used for a variety of acid related disorders. Despite the overall effectiveness and safety profile of PPIs, some patients do not respond adequately or develop treatment related adverse events. This variable response among patients is in part due to genotype variability of CYP2C19, the gene encoding the CYP450 (CYP2C19) isoenzyme responsible for PPIs metabolism.

Areas covered: This article provides an overview of the pharmacokinetics and mechanism of action of the currently available PPIs, including the magnitude of CYPC19 contribution to their metabolism. Additionally, the role of CYP2C19 genetic variability in the therapeutic effectiveness or outcomes of PPI therapy is highlighted in details, to provide supporting evidence for the potential value of CYP2C19 genotype-guided approaches to PPI drug therapy.

Expert opinion: There is a large body of evidence describing the impact of CYP2C19 variability on PPIs and its potential role in individualizing PPI therapy, yet, CYP2C19 pharmacogenetics has not been widely implemented into clinical practice. More data are needed but CYP2C19 genotype-guided dosing of PPIs is likely to become increasingly common and is expected to improve clinical outcomes, and minimize side effects related to PPIs.

Pharmacogenetics: An Important Part of Drug Development with A Focus on Its Application

Since the human genome project in 2003, the view of personalized medicine to improve diagnosis and cure diseases at the molecular level became more real. Sequencing the human genome brought some benefits in medicine such as early detection of diseases with a genetic predisposition, treating patients with rare diseases, the design of gene therapy and the understanding of pharmacogenetics in the metabolism of drugs. This review explains the concepts of pharmacogenetics, polymorphisms, mutations, variations, and alleles, and how this information has helped us better understand the metabolism of drugs. Multiple resources are presented to promote reducing the gap between scientists, physicians, and patients in understanding the use and benefits of pharmacogenetics. Some of the most common clinical examples of genetic variants and how pharmacogenetics was used to determine treatment options for patients having these variants were discussed. Finally, we evaluated some of the challenges of implementing pharmacogenetics in a clinical setting and proposed actions to be taken to make pharmacogenetics a standard diagnostic tool in personalized medicine.

Factors associated with residual gastroesophageal reflux disease symptoms in patients receiving proton pump inhibitor maintenance therapy

AIM

To elucidate the factors associated with residual gastroesophageal reflux disease (GERD) symptoms in patients receiving proton pump inhibitor (PPI) maintenance therapy in clinical practice.

METHODS

The study included 39 GERD patients receiving maintenance PPI therapy. Residual symptoms were assessed using the Frequency Scale for Symptoms of GERD (FSSG) questionnaire and the Gastrointestinal Symptom Rating Scale (GSRS). The relationships between the FSSG score and patient background factors, including the CYP2C19 genotype, were analyzed.

RESULTS

The FSSG scores ranged from 1 to 28 points (median score: 7.5 points), and 19 patients (48.7%) had a score of 8 points or more. The patients’ GSRS scores were significantly correlated with their FSSG scores (correlation coefficient = 0.47, P < 0.005). In erosive esophagitis patients, the FSSG scores of the CYP2C19 rapid metabolizers (RMs) were significantly higher than the scores of the poor metabolizers and intermediate metabolizers (total scores: 16.7 ± 8.6 vs 7.8 ± 5.4, P < 0.05; acid reflux-related symptom scores: 12 ± 1.9 vs 2.5 ± 0.8, P < 0.005). In contrast, the FSSG scores of the CYP2C19 RMs in the non-erosive reflux disease patients were significantly lower than those of the other patients (total scores: 5.5 ± 1.0 vs 11.8 ± 6.3, P < 0.05; dysmotility symptom-related scores: 1.0 ± 0.4 vs 6.0 ± 0.8, P < 0.01).

CONCLUSION

Approximately half of the GERD patients receiving maintenance PPI therapy had residual symptoms associated with a lower quality of life, and the CYP2C19 genotype appeared to be associated with these residual symptoms.

Practical considerations in the management of proton-pump inhibitors

Proton-pump inhibitors (PPIs) are one of the most active ingredients prescribed in Spain. In recent decades there has been an overuse of these drugs in both outpatient clinics and hospitals that has lead to a significant increase in healthcare spending and to an increase in the risk of possible side effects. It is important for health professionals to know the accepted indications and the correct doses for the use of these drugs. On the market there are different types of PPI: omeprazole, pantoprazole, lansoprazole, rabeprazole and esomeprazole. Omeprazole is the oldest and most used PPI, being also the cheapest. Although there are no important differences between PPIs in curing diseases, esomeprazole, a new-generation PPI, has proved to be more effective in eradicating H. pylori and in healing severe esophagitis compared to other PPIs. In recent years the use of generic drugs has spread; these drugs have the same bioavailability than the original drugs. In the case of PPIs, the few comparative studies available in the literature between original and generic drugs have shown no significant differences in clinical efficacy.

[Molecular genetic predictors of resistance to anti-Helicobacter pylori therapy]

In current clinical practice, there is no optimal empirical therapy for Helicobacter pylori (H. pylori) infection and there is a progressive decrease in the efficiency of classical eradication therapy (ET) regimens. The variability in the efficiency of ET in a specific patient is largely due to the heterogeneous molecular genetic mechanisms underlying the resistance of the microorganism to the components of the treatment regimens. The basis of the mechanisms for antibiotic resistance in H. pylori is mainly the point mutations in some genes, which determine alterations in the mechanisms of action of drugs, such as clarithromycin (domain V of 23S rRNA), metronidazole (rdxA, frxA), amoxicillin (pbp1A), tetracycline (16S rRNA), and levofloxacin (gyrA). The predictors of resistance to ET are also the CagA-negative status of the microorganism and the presence of the vacA s2 allele. There are a number of host genetic determinants (the CYP2C19 genotype (*1/*1, *1/*17, *17/*17) and the MDR1 3435 T/T genotype (in an Asian population)) that reduce the efficiency of ET, by altering the pharmacokinetics of proton pump inhibitors. In addition, the IL-1β-511 C/C polymorphism that affects gastric acid secretion is a predictor of the inefficiency of ET.

Rapid metabolizer genotype of CYP2C19 is a risk factor of being refractory to proton pump inhibitor therapy for reflux esophagitis

BACKGROUND

Proton pump inhibitors (PPIs) are mainly metabolized by cytochrome P450 2C19 (CYP2C19) and used as the first-line therapy for gastroesophageal reflux disease (GERD). However, while several studies have examined the influence of CYP2C19 polymorphism on GERD treatment with PPIs, most have had small sample sizes and were conducted in a single center. Here, we used meta-analysis to investigate whether or not the CYP2C19 rapid metabolizer (RM) genotype is a risk factor for GERD patients being refractory to PPI therapy.

METHODS

PubMed and other electronic databases were systematically searched up to August 2014 using the following terms: "GERD and CYP2C19", "esophagitis and CYP2C19", and "non-erosive reflux disease and CYP2C19." Searches were limited to publications in English, and two investigators evaluated eligible studies and extracted data.

RESULTS

The total efficacy rate of PPIs for GERD, including reflux esophagitis (RE) and non-erosive reflux disease, was 56.4% (95% confidence interval [CI]; 53.9-58.9%, 870/1543) in intention-to-treat analysis and 63.8% (95%CI; 61.3-66.2%, 950/1489) in per-protocol analysis. Efficacy rates varied significantly between CYP2C19 genotypes (intention-to-treat analysis: RMs, 52.2% [315/604]; intermediate metabolizers, 56.7% [298/526]; poor metabolizers [PMs], 61.3% [138/225]; P = 0.047). Among RE patients, CYP2C19 RMs had an increased risk of being refractory to PPI therapy compared with PMs (odds ratio: 1.661, 95% CI: 1.023-2.659, P = 0.040).

CONCLUSIONS

The present meta-analysis demonstrates that CYP2C19 RMs with RE have an increased risk of being refractory to PPI therapy compared with PMs. Individualized dosing regimen with PPIs based on CYP2C19 genotype might be a valid therapeutic strategy for overcoming insufficient gastric acid inhibition.

Treatment of Helicobacter Pylori infection: optimization strategies in a high resistance era

INTRODUCTION

Treatment of Helicobacter pylori (H. pylori) infection is paramount for the management of prevalent gastrointestinal disorders and in the prevention of gastric cancer. Due to increasing antimicrobial resistance, performance of standard triple therapies has now declined to unacceptably low levels.

AREAS COVERED

In this article: i) we critically revise optimization tools aiming to improve the outcome of standard treatments; ii) we provide updated evidence on the efficacy and rationale for the use of several non-bismuth quadruple regimens in clinical practice, recommended as preferred empirical therapies in areas of high clarithromycin resistance.

EXPERT OPINION

Prolonged (14-day) treatment duration may boost the efficacy of standard triple therapy by approximately 5%. Use of a high-dose PPI and/or new-generation PPIs, rabeprazole and esomeprazole, might improve eradication rates, particularly in regions where the CYP2C19 rapid metabolizer phenotype is prevalent. Adjunctive probiotics may be considered to improve treatment tolerability, though more data are required to better define their role in H. pylori eradication. Among non-bismuth quadruple regimens, both concomitant and sequential therapies are appropriate options for high-resistance settings; however, concomitant therapy appears to be less impaired by dual clarithromycin/metronidazole resistance. Hybrid therapy is a promising new alternative which seems not to be inferior to concomitant therapy.

Acid-inhibitory effects of vonoprazan 20 mg compared with esomeprazole 20 mg or rabeprazole 10 mg in healthy adult male subjects--a randomised open-label cross-over study

BACKGROUND

Proton pump inhibitors (PPIs) are widely used for the treatment of acid-related diseases. Vonoprazan is a member of a new class of acid suppressants; potassium-competitive acid blockers. Vonoprazan may thus be an alternative to PPIs.

AIM

To evaluate efficacy, rapidity and duration of acid-inhibitory effects of vonoprazan vs. two control PPIs, esomeprazole and rabeprazole, in 20 healthy Japanese adult male volunteers with CYP2C19 extensive metaboliser genotype.

METHODS

In this randomised, open-label, two-period cross-over study, vonoprazan 20 mg and esomeprazole 20 mg (Study V vs. E) or rabeprazole 10 mg (Study V vs. R) were orally administered daily for 7 days. Primary pharmacodynamic endpoint was gastric pH over 24 h measured as percentage of time pH ≥3, ≥4 and ≥5 (pH holding time ratios; HTRs) and mean gastric pH.

RESULTS

Acid-inhibitory effect (pH4 HTR) of vonoprazan was significantly greater than that of esomeprazole or rabeprazole on both Days 1 and 7; Day 7 difference in pH4 HTR for vonoprazan vs. esomeprazole was 24.6% [95% confidence interval (CI): 16.2-33.1] and for vonoprazan vs. rabeprazole 28.8% [95% CI: 17.2-40.4]. The Day 1 to Day 7 ratio of 24-h pH4 HTRs was >0.8 for vonoprazan, compared with 0.370 for esomeprazole and 0.393 for rabeprazole. Vonoprazan was generally well tolerated. One vonoprazan subject withdrew due to a rash which resolved after discontinuation.

CONCLUSIONS

This study demonstrated a more rapid and sustained acid-inhibitory effect of vonoprazan 20 mg vs. esomeprazole 20 mg or rabeprazole 10 mg. Therefore, vonoprazan may be a potentially new treatment for acid-related diseases.

Pharmacogenetics in Jewish populations

Spanning over 2000 years, the Jewish population has a long history of migration, population bottlenecks, expansions, and geographical isolation, which has resulted in a unique genetic architecture among the Jewish people. As such, many Mendelian disease genes and founder mutations for autosomal recessive diseases have been discovered in several Jewish groups, which have prompted recent genomic studies in the Jewish population on common disease susceptibility and other complex traits. Although few studies on the genetic determinants of drug response variability have been reported in the Jewish population, a number of unique pharmacogenetic variants have been discovered that are more common in Jewish populations than in other major racial groups. Notable examples identified in the Ashkenazi Jewish (AJ) population include the vitamin K epoxide reductase complex subunit 1 (VKORC1) c.106G>T (p.D36Y) variant associated with high warfarin dosing requirements and the recently reported cytochrome P450 2C19 (CYP2C19) allele, CYP2C19*4B, that harbors both loss-of-function [*4 (c.1A>G)] and increased-function [*17 (c.-806C>T)] variants on the same haplotype. These data are encouraging in that like other ethnicities and subpopulations, the Jewish population likely harbors numerous pharmacogenetic variants that are uncommon or absent in other larger racial groups and ethnicities. In addition to unique variants, common multi-ethnic variants in key drug metabolism genes (e.g., ABCB1, CYP2C8, CYP2C9, CYP2C19, CYP2D6, NAT2) have also been detected in the AJ and other Jewish groups. This review aims to summarize the currently available pharmacogenetics literature and discuss future directions for related research with this unique population.

A Randomized Study of the Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of Clopidogrel in Three Different CYP2C19 Genotype Groups of Healthy Japanese Subjects

AIM

We investigated the safety of 600/150 mg regimen of clopidogrel and the pharmacodynamics and pharmacokinetics of both 300/75 mg regimen and 600/150 mg regimen of clopidogrel in 72 Japanese subjects.

METHODS

A randomized study was conducted in healthy Japanese male subjects. Eligible subjects were stratified by dose regimen (300 mg loading dose of clopidogrel on day 1 followed by a 75 mg maintenance dose from days 2 to 7 or a 600 mg loading dose of clopidogrel on day 1 followed by a 150 mg maintenance dose from days 2 to 7) and CYP2C19 metabolizer group [extensive metabolizers (EMs), intermediate metabolizers (IMs), and poor metabolizers (PMs)]. Platelet aggregation and platelet reactivity were evaluated by measuring the maximum platelet aggregation intensity (MAI) induced by 5 and 20 μM ADP, phosphorylation of vasodilator-stimulated phosphoprotein (VASP), and P2Y12 reaction units (PRU) using the VerifyNow system, respectively. We also measured the plasma concentrations of clopidogrel and its active metabolite H4.

RESULTS

No treatment emergent adverse events in the 300/75 mg and 600/150 mg regimen were observed in EMs, IMs, and PMs. All CYP metabolizer groups exhibited a lower MAI (%) induced by ADP in the 300/75 mg and 600/150 mg clopidogrel regimens, and MAI (%) in IM group was equipotent to EM irrespective of the clopidogrel dosage. The double dose regimen decreased MAI in the PM group as equipotent to the IM group receiving the standard dose regimen without the extension of bleeding time. No clear relationship of exposure to clopidogrel and CYP2C19 function was observed, whereas active metabolite H4 exposure was likely to be related to CYP2C19 function.

CONCLUSION

Clopidogrel in the 600/150 mg regimen was well tolerated. All CYP metabolizer groups exhibited a lower MAI (%) induced by ADP and anti-platelet activities analyzed by VASP and VerifyNow test in the 300/75 mg and 600/150 mg regimens in healthy Japanese subjects.

A multicentre randomised trial to compare the efficacy of omeprazole versus rabeprazole in early symptom relief in patients with reflux esophagitis

BACKGROUND

Proton pump inhibitors (PPIs) are affected by cytochrome P450 2C19 (CYP2C19) polymorphisms. This study compared the effect of two PPIs on early symptom relief in Japanese patients with reflux esophagitis, classified by the CYP2C19 phenotype.

METHODS

Patients with reflux esophagitis were randomised to treatment with omeprazole 20 mg or rabeprazole 10 mg once daily. The CYP2C19 phenotype [homozygous extensive metaboliser (homoEM), heterozygous extensive metaboliser (heteroEM) or poor metaboliser (PM)] of each patient was determined. The primary efficacy endpoint was early, sufficient (Global Overall Symptom scale score 1 or 2), sustained (maintained for ≥7 days) reflux symptom relief.

RESULTS

Of the 199 patients included in this analysis, the proportion achieving sufficient, sustained reflux symptom relief was higher with omeprazole than with rabeprazole on day 1 (35.6 vs. 22.4%; p = 0.041) and day 2 (43.6 vs. 28.6%; p = 0.028); there was no significant difference between the two groups on days 3-7. Among patients with the CYP2C19 PM phenotype, sufficient, sustained reflux symptom relief was higher with omeprazole than with rabeprazole on days 4-7 (62.5-66.9 vs. 31.6%; p ≤ 0.03); differences were not significant on days 1-3, or among those with the homoEM or heteroEM phenotypes on days 1-7.

CONCLUSIONS

In Japanese patients with reflux esophagitis, omeprazole 20 mg is more effective than rabeprazole 10 mg at achieving early, sufficient, sustained reflux symptom relief in individuals with the CYP2C19 PM phenotype, and is similarly effective to rabeprazole 10 mg in those with heteroEM or homoEM phenotypes.

Prediction of inter-individual variability in the pharmacokinetics of CYP2C19 substrates in humans

Significant inter-individual variability of exposure for CYP2C19 substrates may be only partly due to genetic polymorphism. Therefore, the in vivo inter-individual variability in hepatic intrinsic clearance (CL(int,h)) of CYP2C19 substrates was estimated from reported AUC values using Monte Carlo simulations. The coefficient of variation (CV) for CL(int,h) in poor metabolizers (PM) expected from genotypes CYP2C19*2/*2, CYP2C19*3/*3 or CYP2C19*2/*3 was estimated as 25.8% from the CV for AUC of omeprazole in PMs. With this, CVs of CL(int,h) in extensive metabolizers (EM: CYP2C19*1/*1), intermediate metabolizers (IM: CYP2C19*1/*2 or *3) and ultra-rapid metabolizers (UM), CYP2C19*17/*17 and *1/*17, were estimated as 66.0%, 55.8%, 6.8% and 48.0%, respectively. To validate these CVs, variability in the AUC of CYP2C19 substrates lansoprazole and rabeprazole, partially metabolized by CYP3A4 in EMs and IMs, were simulated using the CV in CL(int,h) for CYP2C19 EMs and IMs and 33% of the CV previously reported for CYP3A4. Published values were within 2.5-97.5 percentile range of simulated CVs for the AUC. Furthermore, simulated CVs for the AUC of omeprazole and lansoprazole in ungenotyped populations were comparable with published values. Thus, estimated CL(int,h) variability can predict variability in the AUC of drugs metabolized not only by CYP2C19 but also by multiple enzymes.

Eradication of H. pylori infection in patients allergic to penicillin using triple therapy with a PPI, metronidazole and sitafloxacin

Eradication of H. pylori in patients allergic to penicillin should be performed using regimens without penicillin derivatives. We treated a total of 28 patients allergic to penicillin with a proton pump inhibitor (PPI), metronidazole (250 mg bid) and sitafloxacin (100 mg bid) for one to two weeks. At four to eight weeks after the treatment, the patients underwent the [(13)C]-urea breath test. The overall eradication rate was 100.0%. Mild adverse events were observed. Triple therapy with a PPI, metronidazole and sitafloxacin is well tolerated and effective for the eradication of H. pylori in patients allergic to penicillin.

Genetic Polymorphism of Cytochrome p450 (2C19) Enzyme in Iranian Turkman Ethnic Group

OBJECTIVE

Different findings indicate that CYP2C plays a clinical role in determining interindividual and interethnic differences in drug effectiveness. The ethnic differences in the frequency of CYP2C19 mutant alleles continue to be a significant study topic. The aim of the present study was to assess the frequency of allelic variants of CYP2C19 in Turkman ethnic groups and compare them with the frequencies in other ethnic populations.

METHODS

The study group included 140 unrelated healthy ethnic Turkman subject referred to the Health Center. Genotyping of CYP2C19 alleles (CYP2C19*1, CYP2C19*2, and CYP2C19*3 alleles) was carried out by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism technique.

RESULTS

The allele frequency of CYP2C19*1, CYP2C19*2 and CYP2C19*3 were 56.43%, 23.57% and 20%, respectively. The result also showed that 39.7% of subjects expressed the CYP2C19*1/*1 genotype. While 42.1%, 9.3%, 9.3% and 1.4% expressed CYP2C19*1/*2, CYP2C19*1/*3, CYP2C19*2/*2 and CYP2C19*3/*3 genotypes, respectively. The genotype CYP2C19*2/*3 was not expressed in this study population. The findings suggested that 10% of subjects were poor metabolizers by expressing CYP2C19*2/*2 and CYP2C19*3/*3 genotypes. Fifty one percent of subjects were intermediate metabolizers having CYP2C19*1/*2, CYP2C19*2/*3 and CYP2C19*1/*3 genotypes and 37.86% were found to be extensive metabolizers expressing CYP2C19*1/*1 genotype. The frequency of intermediate metabolizers genotype was high (51%) in Turkman ethnic groups.

CONCLUSION

This study showed that the determined allelic variants of CYP2C19 (CYP2C19*2 and CYP2C19*3 mutations) in Turkman ethnic group are comparable to other populations. These findings could be useful for the clinicians in different country to determine optimal dosage and effectiveness of drugs metabolized by this polymorphic enzyme.

Randomized trial comparing rabeprazole- versus lansoprazole-based Helicobacter pylori eradication regimens

Different types of proton pump inhibitor (PPI)-based triple therapies could result in different Helicobacter pylori eradication rates. This study aimed to compare the efficacy and safety of rabeprazole- and lansoprazole-based triple therapies in primary treatment of H. pylori infection. From September 2005 to July 2008, 426 H. pylori-infected patients were randomly assigned to receive a 7-day eradication therapy with either rabeprazole 20mgbid (RAC group, n=222) or lansoprazole 30mgbid (LAC group, n=228) in combination with amoxicillin 1gbid and clarithromycin 500mgbid. The patients received follow-up esophagogastroduodenoscopy (EGD) and/or (13)C-urea breath test 12-16 weeks later to define H. pylori status. Their personal and medical history, compliance and side effects were obtained by using a standardized questionnaire. Intention-to-treat analysis revealed that the eradication rate was 87.84% in the RAC group and 85.96% in the LAC group (p=0.56). All patients returned for assessment of compliance (100% in the LAC group vs. 99.50% in the RAC group; p=0.32) and adverse events (7.20% in the RAC group vs. 5.70% in the LAC group, p=0.51). Univariate analysis suggested that patients with nonsteroid anti-inflammatory agent (NSAID) use had lower eradication rates than those without (76.71% vs. 88.74%; p=0.006). Our results showed that efficacy and safety were similar in rabeprazole- and lansoprazole-based primary therapies. The influence of NSAID usage on H. pylori eradication needs to be further investigated.

In vivo quantitative prediction of the effect of gene polymorphisms and drug interactions on drug exposure for CYP2C19 substrates

We present a unified quantitative approach to predict the in vivo alteration in drug exposure caused by either cytochrome P450 (CYP) gene polymorphisms or CYP-mediated drug-drug interactions (DDI). An application to drugs metabolized by CYP2C19 is presented. The metrics used is the ratio of altered drug area under the curve (AUC) to the AUC in extensive metabolizers with no mutation or no interaction. Data from 42 pharmacokinetic studies performed in CYP2C19 genetic subgroups and 18 DDI studies were used to estimate model parameters and predicted AUC ratios by using Bayesian approach. Pharmacogenetic information was used to estimate a parameter of the model which was then used to predict DDI. The method adequately predicted the AUC ratios published in the literature, with mean errors of -0.15 and -0.62 and mean absolute errors of 0.62 and 1.05 for genotype and DDI data, respectively. The approach provides quantitative prediction of the effect of five genotype variants and 10 inhibitors on the exposure to 25 CYP2C19 substrates, including a number of unobserved cases. A quantitative approach for predicting the effect of gene polymorphisms and drug interactions on drug exposure has been successfully applied for CYP2C19 substrates. This study shows that pharmacogenetic information can be used to predict DDI. This may have important implications for the development of personalized medicine and drug development.

The effects of varying acidity on Helicobacter pylori growth and the bactericidal efficacy of ampicillin

BACKGROUND

Penicillins inhibit cell wall synthesis; therefore, Helicobacter pylori must be dividing for this class of antibiotics to be effective in eradication therapy. Identifying growth responses to varying medium pH may allow design of more effective treatment regimens.

AIM

To determine the effects of acidity on bacterial growth and the bactericidal efficacy of ampicillin.

METHODS

H. pylori were incubated in dialysis chambers suspended in 1.5-L of media at various pHs with 5 mM urea, with or without ampicillin, for 4, 8 or 16 h, thus mimicking unbuffered gastric juice. Changes in gene expression, viability and survival were determined.

RESULTS

At pH 3.0, but not at pH 4.5 or 7.4, there was decreased expression of ~400 genes, including many cell envelope biosynthesis, cell division and penicillin-binding protein genes. Ampicillin was bactericidal at pH 4.5 and 7.4, but not at pH 3.0.

CONCLUSIONS

Ampicillin is bactericidal at pH 4.5 and 7.4, but not at pH 3.0, due to decreased expression of cell envelope and division genes with loss of cell division at pH 3.0. Therefore, at pH 3.0, the likely pH at the gastric surface, the bacteria are nondividing and persist with ampicillin treatment. A more effective inhibitor of acid secretion that maintains gastric pH near neutrality for 24 h/day should enhance the efficacy of amoxicillin, improving triple therapy and likely even allowing dual amoxicillin-based therapy for H. pylori eradication.

Distribution of CYP2D6 and CYP2C19 polymorphisms associated with poor metabolizer phenotype in five Amerindian groups and western Mestizos from Mexico

BACKGROUND

The distribution of polymorphisms in the CYP2D6 and CYP2C19 genes allows inferring the potential risk for specific adverse drug reactions and lack of therapeutic effects in humans. This variability shows differences among human populations. The aim of this study was to analyze single-nucleotide polymorphisms related to a poor metabolizer (PM) phenotype in nonpreviously studied Amerindian groups and Mestizos (general admixed population) from Mexico.

METHODS

We detected by SNaPshot(®) different polymorphisms located in CYP2D6 (*3, *4, *6, *7, and *8) and CYP2C19 (*2, *3, *4 and *5) in western Mestizos (n=145) and five Amerindian groups from Mexico: Tarahumaras from the North (n=88); Purépechas from the Center (n=101); and Tojolabales (n=68), Tzotziles (n=88), and Tzeltales (n=20) from the Southeast. Genotypes were observed by capillary electrophoresis. The genetic relationships among these populations were estimated based on these genes.

RESULTS AND DISCUSSION

The wild-type allele (*1) of both genes was predominant in the Mexican populations studied. The most widely observed alleles were CYP2C19*2 (range, 0%-31%) and CYP2D6*4 (range, 1.2%-7.3%), whereas CYP2D6*3 was exclusively detected in Mestizos. Conversely, CYP2C19*4 and *5, as well as CYP2D6*3, *6, *7, and *8, were not observed in the majority of the Mexican populations. The Tarahumaras presented a high frequency of the allele CYP2C19*2 (31%) and of homozygotes *2/*2 (10.7%), which represent a high frequency of potentially PM phenotypes in this Amerindian group. The genetic distances showed high differentiation of Tarahumaras (principally for CYP2C19 gene). In general, a relative proximity was observed between most of the Amerindian, Mexican-Mestizo, and Latin-American populations.

CONCLUSION

In general, the wild-type allele (*1) predominates in Mexican populations, outlining a relatively homogeneous distribution for CYP2C19 and CYP2D6. The exception is the Tarahumara group that displays a potentially increased risk for adverse reactions to CYP2C19-metabolized drugs.

Evaluation of Six Cases of Idiopathic Gastric Antral Ulcer

Six cases of gastric antral ulcer with an unknown cause encountered at our hospital and related facilities during the last 5 years were evaluated. The frequency of the disease was 1.3% of all gastric ulcers. The lesions were multiple in 3 and solitary in 3. All these lesions were ellipsoidal and small ulcers 1 cm or less in long diameter with mucosal elevations around them, located primarily in the greater curvature, and accompanied by reddened erosions in other areas of the antrum. The patients were middle-aged or older, 5 of them were females, half of them had a history of bleeding, and 4 showed resistance to treatment with proton pump inhibitors. The 6 patients had common clinical features, suggesting that they had the same disease. From the presence of reddened erosion, mutual friction of the antral mucosa was suspected to be a cause of the disease. Similar ulcers are found in the literature, but they have not been described or evaluated in detail. The further accumulation of cases and clarification of details of the disease are desired.

Helicobacter pylori: Eradication or Preservation

Helicobacter pylori infects about 50% of the world's population and inevitably results in the development of gastritis. Of those infected, about 10% develop peptic ulcer disease and roughly 1% develop gastric cancer. Conversely, some take the view that H. pylori infection provides some protection against gastro-esophageal reflux disease and possibly asthma. This review aims to explore the case for and against eradication of the bacterium using a "test and treat" approach amongst the general population.

Gastric infection by Helicobacter pylori

Helicobacter pylori infects half of the world's population and plays a causal role in ulcer disease and gastric cancer. This pathogenic neutralophile uniquely colonizes the acidic gastric milieu through the process of acid acclimation. Acid acclimation is the ability of the organism to maintain periplasmic pH near neutrality in an acidic environment to prevent a fall in cytoplasmic pH in order to maintain viability and growth in acid. Recently, due to an increase in antibiotic resistance, the rate of H. pylori eradication has fallen below 80% generating renewed interest in novel eradication regimens and targets. In this article, we review the gastric biology of H. pylori and acid acclimation, various detection procedures, antibiotic resistance and the role that gastric acidity plays in the susceptibility of the organism to antibiotics currently in use and propose several novel drug targets that would promote eradication in the absence of antibiotics.

Acid inhibition effect of ilaprazole on Helicobacter pylori-negative healthy volunteers: an open randomized cross-over study

OBJECTIVE

The aim of this study was to evaluate the effects and safety of different doses of ilaprazole on healthy volunteers without a Helicobacter pylori infection.

METHODS

A total of 12 healthy Chinese volunteers were enrolled and divided into four groups randomly, with a 5-day treatment of oral ilaprazole 5mg, 10mg and 20mg or omeprazole 20mg, respectively. After an interval of a 14-day washout phase, each was switched to another dose group and eventually completed all four regimens. The percentage time of intragastric pH>4 was the major index. The polymorphisms of the metabolic enzyme CYP2C19 in these volunteers were also detected.

RESULTS

The percentage time of intragastric pH>4 in the ilaprazole 5, 10 and 20mg groups were 80.4%, 88.1% and 91.0%, respectively, during the first 24h, compared to that of the 20mg omeprazole group (76.6%, P>0.05). Ilaprazole 20mg provided a significant higher mean 24-h pH than that of the same dose of omeprazole both on Day 1 (7.78 vs 6.67, P<0.01) and Day 5 (7.95 vs 7.44, P<0.05). No CYP2C19-dependent difference or obvious adverse effect were found in any ilaprazole groups.

CONCLUSION

Low dose ilaprazole offers a gastric acid inhibition comparable to a routine dose of omeprazole, and further investigations in patients with acid-associated diseases are needed.

Similarities and differences between US and Japan as to pharmacogenomic biomarker information in drug labels

Pharmacogenomics (PGx) has been utilized as a tool to improve a drug's benefit/risk ratio and the efficiency of drug developments. In order to examine what factors are involved to determine the level of contexts (contents and descriptions) of drug-PGx biomarker information, we graded sections of Japanese package inserts and US drug labels into six levels according to the importance of cautions in regards to clinical practice and compared similarities and differences of the contexts between the two countries. Out of 54 contexts identified, 33 (61%) were graded differently between Japan and the US. The different contexts were mainly related to metabolizing enzymes used in terms of safety, therapeutic areas other than oncology, outcome before 1993, Japan-based companies having marketing authorization and no PGx data on the Japanese population. We describe the potential reasons that could lead to the differences between the two countries such as genetic differences and quantitative evidence in the Japanese population, and also discuss future perspectives to improve PGx utilization in clinical practices in Japan.

Clinical usefulness of limited sampling strategies for estimating AUC of proton pump inhibitors

Cytochrome P450 (CYP) 2C19 (CYP2C19) genotype is regarded as a useful tool to predict area under the blood concentration-time curve (AUC) of proton pump inhibitors (PPIs). In our results, however, CYP2C19 genotypes had no influence on AUC of all PPIs during fluvoxamine treatment. These findings suggest that CYP2C19 genotyping is not always a good indicator for estimating AUC of PPIs. Limited sampling strategies (LSS) were developed to estimate AUC simply and accurately. It is important to minimize the number of blood samples because of patient's acceptance. This article reviewed the usefulness of LSS for estimating AUC of three PPIs (omeprazole: OPZ, lansoprazole: LPZ and rabeprazole: RPZ). The best prediction formulas in each PPI were AUC(OPZ)=9.24 x C(6h)+2638.03, AUC(LPZ)=12.32 x C(6h)+3276.09 and AUC(RPZ)=1.39 x C(3h)+7.17 x C(6h)+344.14, respectively. In order to optimize the sampling strategy of LPZ, we tried to establish LSS for LPZ using a time point within 3 hours through the property of pharmacokinetics of its enantiomers. The best prediction formula using the fewest sampling points (one point) was AUC(racemic LPZ)=6.5 x C(3h) of (R)-LPZ+13.7 x C(3h) of (S)-LPZ-9917.3 x G1-14387.2×G2+7103.6 (G1: homozygous extensive metabolizer is 1 and the other genotypes are 0; G2: heterozygous extensive metabolizer is 1 and the other genotypes are 0). Those strategies, plasma concentration monitoring at one or two time-points, might be more suitable for AUC estimation than reference to CYP2C19 genotypes, particularly in the case of coadministration of CYP mediators.

Identification of CYP2C19*4B: pharmacogenetic implications for drug metabolism including clopidogrel responsiveness

CYP2C19 is a principal enzyme involved in the bioactivation of the antiplatelet prodrug clopidogrel and common CYP2C19 loss-of-function alleles are associated with adverse cardiovascular events. To assess the impact of the CYP2C19*17 increased activity allele in the Ashkenazi Jewish (AJ) and Sephardi Jewish (SJ) populations and to determine the frequencies of additional variant alleles, 250 AJ and 135 SJ individuals were genotyped for CYP2C19*2-*10, *12-*17, *22 and P-glycoprotein (ABCB1) c.3435C>T. Importantly, CYP2C19*4, a loss-of-function allele, was identified in linkage disequilibrium with *17. This novel haplotype, designated CYP2C19*4B, significantly alters the interpretation of CYP2C19 genotyping when testing *17. Moreover, genotyping CYP2C19*17 changed the frequency of extensive metabolizers from ∼70 to ∼40%, reclassifying ∼30% as ultrarapid metabolizers. Combining CYP2C19 and ABCB1 identified ∼1 in 3 AJ and ∼1 in 2 SJ individuals at increased risk for adverse responses to clopidogrel. These data underscore the importance of including *4B and *17 when clinically genotyping CYP2C19.

Review article: combination of clopidogrel and proton pump inhibitors: implications for clinicians

OBJECTIVES

to evaluate the existing literature on a proposed interaction between clopidogrel and proton pump inhibitors (PPIs) and discuss its implications for clinicians treating patients with this combination therapy.

BACKGROUND

each year millions of patients receive antiplatelet therapy. A number of these patients are prescribed PPIs concomitantly to reduce the risk of gastrointestinal side effects associated with antiplatelet therapy. Several studies have been published recently addressing a potential adverse drug-drug interaction between clopidogrel and PPIs.

METHODS

literature was evaluated through Pubmed using the terms clopidogrel, PPI, prasugrel, cytochrome P450, genetic polymorphisms, H( 2) blockers, famotidine, genetic cytochrome P450 polymorphisms, and drug interaction. Articles with these terms were considered for evaluation. In addition, reference citations from publications identified in the searches were further reviewed and analyzed.

RESULTS

none of the currently published studies were specifically designed to evaluate this drug-drug interaction or address the clinical relevance of this interaction prospectively. Conflicting evidence raised concerns but the information did not conclude with certainty a cause-and-effect relationship between concomitant use of the drugs and emerging safety issues. However, the Food and Drug Administration issued a public-health warning on the possible interaction between clopidogrel and PPIs, predominantly with omeprazole, in November 2009.

CONCLUSIONS

controversies exist on a potential drug-drug interaction between clopidogrel and PPIs. Although further studies are warranted, several studies indicated that there was a drug-drug interaction through this combination therapy with detrimental clinical outcomes and increased costs. Studies suggested that the use of a PPI may make clopidogrel less effective resulting in a higher risk of myocardial infarction, stroke, or death. Until additional information becomes available clinicians should consider discontinuing PPI use if no clear indication is documented. Alternative options like H(2)-receptor antagonists should be considered. Upon availability, genetic testing may provide additional valuable information.